Thyrotropin Releasing Hormone (TRH) reverses the hypotensive effect of the angiotensin converting enzyme inhibitor, Captopril, on the Goldblatt 2 kidney, 1 clip (2K/1C) model of renal hypertension in the rat. The tripeptide also reverses the hypotension induced by the i.v. infusion of nitroglycerin, but fails to modify the depressor effect of neurotensin. Serotonin depletion abolishes the hkypertensive effect of TRH in captoril treated 2K/1C rats.